Petrogenesis and structural petrology of high-pressure metabasalt pods,Sivrihisar, Turkey |
| |
| Authors: | Peter B Davis Donna L Whitney |
| |
| Institution: | (1) Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA |
| |
| Abstract: | Lawsonite eclogite pods ranging in size from 3 cm to 6 m occur in lawsonite blueschist and eclogite facies metasedimentary
and metabasaltic rocks in the Sivrihisar Massif, Turkey. Some pods have a core of lawsonite eclogite surrounded by alternating,
centimeter-scale layers of lawsonite blueschist, eclogite, and transitional eclogite–blueschist, all with similar basaltic
bulk composition. These pods also contain texturally late lawsonite-rich veins and layers. Most eclogites and blueschists
within the pods lack reaction textures, but some blueschists near pod margins contain texturally complex garnet as well as
glaucophane rims on omphacite, suggesting retrogression of eclogite to blueschist. Phase diagrams (pseudosections) calculated
for the lawsonite eclogite core of a meter-scale pod indicate that the eclogite equilibrated at ∼22–24 kbar, ∼520°C. Lawsonite
eclogite and blueschist at the tectonized margin of the same pod equilibrated at similar temperatures and slightly lower pressures.
The composite eclogite–blueschist pod is foliated, lineated, and folded. An earlier generation of lineated omphacite in the
pod core has a different spatial orientation than the lineation at the pod margin, although electron backscattered diffraction
data show that core and rim omphacite have similar lattice preferred orientation patterns. Petrologic and structural data
are consistent with mechanical formation of pods by folding and dissection of eclogite layers at high-P, and localized retrogression at pod margins during initial stages of exhumation at P–T conditions >425°C, 16 kbar. |
| |
| Keywords: | Blueschist Eclogite High-pressure Sivrihisar Turkey |
| 本文献已被 SpringerLink 等数据库收录！ |
|
